code: def test_round_int_str():
      assert round_number_str(0.951) == "1"
      assert round_number_str(0.95) == "0.9"
      assert round_number_str(0.949) == "0.9"
      assert round_number_str(0.00949) == "0.009"
      assert round_number_str(0.00950) == "0.009"
      assert round_number_str(0.00951) == "0.01"
      assert round_number_str(0.0044) == "0.004"
      assert round_number_str(0.00451) == "0.005"
      assert round_number_str(0.0001) == "0.0001"
      assert round_number_str(0.00001) == "1e-05"
      assert round_number_str(0.000000321) == "3e-07"
      assert round_number_str(12_000) == "12k"
      assert round_number_str(13_340) == "13k"
      assert round_number_str(13_540) == "14k"
      assert round_number_str(559_540) == "560k"
      assert round_number_str(949_000) == "949k"
      assert round_number_str(950_000) == "950k"
      assert round_number_str(950_001) == "1M"
      assert round_number_str(1_950_001) == "2M"
      assert round_number_str(111_950_001) == "112M"
      assert round_number_str(950_001_001) == "1B"
      assert round_number_str(1_950_001_001) == "2B"
      assert round_number_str(111_950_001_001) == "112B"
      assert round_number_str(950_001_001_001) == "1T"
      assert round_number_str(1_950_001_001_001) == "2T"
      assert round_number_str(111_950_001_001_001) == "112T"
      # zero should return None
      assert round_number_str(0) is None
      # negative case
      assert round_number_str(-0.951) == "-1"
      assert round_number_str(-0.95) == "-0.9"
  
file_path: plotly-resampler/tests/test_utils.py
imports: import pandas
  import plotly.graph_objects
  from plotly_resampler import FigureResampler, FigureWidgetResampler
  from plotly_resampler.figure_resampler.utils import is_figure, is_figurewidget, is_fr, is_fwr, round_number_str, round_td_str, timedelta_to_str
label_desc: Use image node_id 6 for calling a global function with example usage: test_round_int_str() without return types